Spark plug shield



April 1964 s. E. ESTES 3,128,139

SPARK PLUG SHIELD Filed June 27, 1960 INV TOR. SrAM/LEY $755 wid/ ml iplug 11.

United States Patent Ofi ice 3,128,139 Patented Apr. 7., 1964 3,128,139SPARK PLUG SHIELD Stanley E. Estes, Inglewood, Califi, assignor toHallett Manufacturing Company, Los Angeles, Calif., a corporation ofCalifornia a Filed June 27, 1960, Ser. No. 38,976 8 Claims. (Cl. 339-26)boats, as well as in stationary installations embodying radio equipmentwhere these installations are proximate internal combustion enginesseriously diminishes the utility of the radio receiving and transmittingapparatus.

By enclosing thevarious elements of the ignition system within ametallic electrically conductive housing which is grounded, theelectrical radiations from the sys' tem will be dissipated in the groundand the interference eliminated. In the case of spark plugs themselvesthey have been shielded by building a metallic housing into the plugitself which is expensive and not otherwise fully satisfactory. Iam alsoaware of a separate spark plug housing, but this type renders the sparkplug ditficult of access 'as well as other faults which I haveeliminated by my present invention.

A broad object of my inventionis to provide a compact electricalshielding for a spark plug which will substantially prevent transmissionof electricalradiation.

A further object of my invention is to provide an improved shielding fora spark plug which serves the additional function of physical protectionagainst weather.

, Still another object of my invention is to provide a spark plug shieldof light weight, simple construction, and which can be readily assembledor disassembled and which nevertheless serves thefunction of shieldingwith maximum efiiciency: Y 7

Still another object of my invention is to provide a new and improvedshield for a spark plug which incorporates a simplified mounting on thespark plug permitting it to be installed on the plug and removedwithoutthe use of special tools.

With these and-other objects in'view, the invention consists in theconstruction, arrangement and combination of the various parts of thedevice whereby the objects contemplated are attained as hereafter morefully set forth, pointed out in the claims, and illustrated in theaccompanying drawings,'in which:

FIGURE 1 is a side elevational cross section view of my spark plugshield;

FIGURE 2is a view similar to FIGURE 1 wherein the shield is mounted on aspark plug;

FIGURE 3 is a cross section taken on line 3--3 of FIGURE 2.

My spark plug shield is indicated by the reference numeral which isadapted to fit on a spark plug 11 which is installed in a cylinder head12 of an internal combustion engine.

The spark plug shield comprises an enlarged tubular electricallyconductive housing 13 of sufiicient diameter to accommodate thehexagonal shoulder 14 of the spark The upper portion of the tubularhousing 13 is tapered forming a conical neck portion 15 and acylindrical end portion 16 having an inside diameter suflicient toreceive an electrical cable 17 An insulating member 20 is formed with anannular 2. shoulder 21 at its upper end resting against the upper end ofconical neck portion 15 of the tubular housing 13. The insulating member20 extends downward from the annular shoulder 21 to a position in thetubular housing 13 shown in FIGURESl and 2. The insulating member 20ends has an annular shoulder portion 22 with a diameter substantiallythe same asthe inside diameter of the tubularhousing 13 so that when theinsulating member 20 is inserted in the tubular housing 13 the shoulder22 will engage the interior of the housing 13 and frictionally hold itin position as illustrated in FIGURES l and 2. It should be noted thatto insure permanency the shoulder 22 may be cemented to the interior ofthe housing 13. The insulating member 20 is further formed with anopening 23 extending through the insulator. The central portion of theinsulator opening 23 is enlarged at 24 to receive the electrode terminal25 and porcelain insulator 26 of the spark plug. The elongated enlargedportion 24 is substantially the same diameter throughout but at itslower end is reduced in diameter forming an annual gripping portion 24'which will accommodate and frictionally engage ribs 27 of the'spark plug11, or in the case of spark plugs having smooth surfaced insulators, thesmooth surface will be engaged by gripping portion 24'. It should benoted that the diameter of the central portion 24 is Wider than theinsulator portion 26 when inserted and there is formed an annular airspace around the insulator portion 26. This air space creates an airthermal insulation between the spark plug insulator and the spark plugshield, thus'maintaining a relatively loW temperature on the exterior ofthe shield. An elongated electrical grounding spring clip 28 ispositioned between the annular shoulder 22 of the insulator and theinside surface of the tubular housing 13. This clip 28extends downwardparallel to and engaging the housing 13 to a pointwhere it is bentinward forming a portion 29 which engages the hexagonal shoulder 14 ofthe spark plug 11 as best shown in FIGURE 2. With the use of thisgrounding spring clip 28 any electrical radiation which may be travelingalong the tubular housing 13 will pass to the clip, then to the metalshell of the spark plug and thence to the cylinder head 12.

At the upper end of the enlarged opening 24 of the insulator anoutwardly extending annular shoulder 30 of a terminal conductiveconnector 32'engages a shoulder 31 of the insulator. An upper threadedscrew portion 33 of connector 32 is threaded into the wire end portion34 of cable 17. A nonconductive collar 35 is fitted around the cable 17in the opening 23 to further hold the cable in position on the connector32.

The cable 17 extends upward from the connector 32 snugly through theopening 23 in the insulator and out the elongate cylindrical end portion16 to an electrical distributor cap not shown.

The cable 17 between the distributor cap and the end portion 16 of thehousing is shielded with tinned copper braid 36 which affordssubstantial metallic conductive coverage of the cable. The braid or mesh36 does not enter the end portion 16 but is spread so that it will fitover the end portion 16 as shown in FIGURES l and 2. An outer collar 37is fitted and crimped over the mesh to hold it to the neck portion 16.Thus by the contact of the mesh with the portion 16 of tubular housing13 the grounding of any electrical radiation will be complete from thebraid to the tubular housing to the spark plug to the motor.

While the invention has been shown and described herein in What isconceived to be the most practical and preferred embodiment, itisrecognized that departures may be made therefrom within the scope ofthe invention which is therefore not to be limited to the detailsdisclosed hereat a point at least midway between the respective.

in but is to be accorded the full scope of the claims and so as toembrace any and all equivalent apparatus.

Having described my invention, what I claim as new and desire to secureby Letters Patent is:

1. Electrical shielding means for use with a spark plug of an internalcombustion engine which spark plug comprises a conductive shellincluding a wrench shoulder formed thereon, a porcelain insulatormounted on said shell and an electrode terminal projecting from saidinsulator, said electrical shielding means comprising an electricallyconductive tubular housing including a first open ended section ofrelatively large diameter adapted to receive the spark plug, a secondopen ended section of relatively small diameter, and an intermediatesection conductively connected with the first and second sections, aninsulator member mounted within said housing including an annularenlarged portion engaging said tubular housing and reduced portionsprojecting from said enlarged portion into said intermediate section andsaid first open ended section respectively, said reduced portionsradially spaced from said intermediate section and said first open endedsection respectively of said housing, said insulator member formed witha bore extending entirely therethrough, said bore including an annularend portion which is adapted to frictionally engage a section of theporcelain insulator spaced from said wrench shoulder, whereby saidhousing is adapted to be retained in spaced relation from said sparkplug, an electrode terminal conductive cap mounted in said insulatorbore adapted to frictionally engage said electrode terminal andstabilize said tubular housing about said spark plug, an insulatedconductive cable extending through said second open ended section andsaid insulator bore and conductively connected with said electrodeterminal cap, said cable being provided with external conductivesheathing terminating on the second open ended section and conductivelyconnected thereto and providing electrical grounding therewith, and asecond ground connection extending from the housing adapted to engagethe conductive shell of said spark plug.

2. Electrical shielding means as defined in claim 1 wherein said secondground connection is a conductive spring clip engageable with the wrenchshoulder of said spark plug.

3. Electrical shielding means as defined in claim 1 wherein the axis ofeach of said first open ended section, said second open ended sectionand said intermediate section lie on the same line.

4. Electrical shielding means as defined in claim 3 wherein saidintermediate section is tapered from said second open ended section tosaid first open ended section.

5. The combination of: a spark plug for an internal combustion enginecomprising an electrically conductive shell including a wrench shoulderformed thereon, a porcelain insulator mounted on said shell and anelectrode terminal projecting from said insulator, an electricallyconductive tubular housing including a first open ended section ofrelatively large diameter receiving the spark plug, a second open endedsection of relatively small diameter, and an intermediate sectionconductively connected with the first and second sections, an insulatormember mounted within said housing including an annular enlarged portionengaging said tubular housing and reduced portions projecting from saidenlarged portion into said intermediate section and said first openended section respectively, said reduced portions radially spaced fromsaid intermediate section and said first open ended section respectivelyof said housing, said insulator member formed with a bore extendingentirely therethrough, said bore including an annular end portion whichfrictionally engages a section of the porcelain insulator spaced fromsaid wrench shoulder, whereby said housing is retained in spacedrelation from said spark plug, an electrode terminal conductive capmounted in said insulator bore to frictionally engage said electrodeterminal and stabilize said tubular housing about said spark plug, aninsulated conductive cable extending through said second open endedsection and said insulator bore and conductively connected with saidelectrode terminal cap, said cable being provided with externalconductive sheathing terminating on the second open ended section andconductively connected thereto and providing electrical groundingtherewith, and a second ground connection extending from the housingengaging the conductive shell of said spark plug.

6. The combination as defined in claim 5 wherein said second groundconnection is a conductive spring clip engageable with the wrenchshoulder of said spark plug.

7. The combination as defined in claim 5 wherein the axis of each ofsaid first open ended section, said second open ended section, and saidintermediate section lie on the same line.

8. The combination as defined in claim 5 wherein said intermediatesection is tapered from said second open ended section to said firstopen ended section.

References Cited in the file of this patent UNITED STATES PATENTS1,167,820 Herz Jan. 11, 1916 1,765,443 Peterson June 24, 1930 1,909,248Benkelman May 16, 1933 2,071,572 Rabezzana et al Feb. 23, 1937 2,113,590Hiscock Apr. 12, 1938 2,133,789 Pool Oct. 18, 1938 2,286,918 MascuchJune 16, 1942 2,296,054 Rabezzana Sept. 15, 1942 2,673,233 SalisburyMar. 23, 1954 2,730,562 Marden Ian. 10, 1956 2,863,131 Carlzen et al.Dec. 2, 1958 2,876,274 Cole et al. Mar. 3, 1959 FOREIGN PATENTS 167,659Great Britain Aug. 18, 1921 374,948 Great Britain June 20, 1932 231,329Switzerland June 1, 1944 146,131

Australia Dec. 22, 1949

1. ELECTRICAL SHIELDING MEANS FOR USE WITH A SPARK PLUG OF AN INTERNALCOMBUSTION ENGINE WHICH SPARK PLUG COMPRISES A CONDUCTIVE SHELLINCLUDING A WRENCH SHOULDER FORMED THEREON, A PORCELAIN INSULATORMOUNTED ON SAID SHELL AND AN ELECTRODE TERMINAL PROJECTING FROM SAIDINSULATOR, SAID ELECTRICAL SHIELDING MEANS COMPRISING AN ELECTRICALLYCONDUCTIVE TUBULAR HOUSING INCLUDING A FIRST OPEN ENDED SECTION OFRELATIVELY LARGE DIAMETER ADAPTED TO RECEIVE THE SPARK PLUG, A SECONDOPEN ENDED SECTION OF RELATIVELY SMALL DIAMETER, AND AN INTERMEDIATESECTION CONDUCTIVELY CONNECTED WITH THE FIRST AND SECOND SECTIONS, ANINSULATOR MEMBER MOUNTED WITHIN SAID HOUSING INCLUDING AN ANNULARENLARGED PORTION ENGAGING SAID TUBULAR HOUSING AND REDUCED PORTIONSPROJECTING FROM SAID ENLARGED PORTION INTO SAID INTERMEDIATE SECTION ANDSAID FIRST OPEN ENDED SECTION RESPECTIVELY, SAID REDUCED PORTIONSRADIALLY SPACED FROM SAID INTERMEDIATE SECTION AND SAID FIRST OPEN ENDEDSECTION RESPECTIVELY OF SAID HOUSING, SAID INSULATOR MEMBER FORMED WITHA BORE EXTENDING ENTIRELY THERETHROUGH, SAID BORE INCLUDING AN ANNULAREND PORTION WHICH IS ADAPTED TO FRICTIONALLY ENGAGE A SECTION OF THEPORCELAIN INSULATOR SPACED FROM SAID WRENCH SHOULDER, WHEREBY SAIDHOUSING IS ADAPTED TO BE RETAINED IN SPACED RELATION FROM SAID SPARKPLUG, AN ELECTRODE TERMINAL CONDUCTIVE CAP MOUNTED IN SAID INSULATORBORE ADAPTED TO FRICTIONALLY ENGAGE SAID ELECTRODE TERMINAL ANDSTABILIZE SAID TUBULAR HOUSING ABOUT SAID SPARK PLUG, AN INSULATEDCONDUCTIVE CABLE EXTENDING THROUGH SAID SECOND OPEN ENDED SECTION ANDSAID INSULATOR BORE AND CONDUCTIVELY CONNECTED WITH SAID ELECTRODETERMINAL CAP, SAID CABLE BEING PROVIDED WITH EXTERNAL CONDUCTIVESHEATHING TERMINATING ON THE SECOND OPEN ENDED SECTION AND CONDUCTIVELYCONNECTED THERETO AND PROVIDING ELECTRICAL GROUNDING THEREWITH, AND ASECOND GROUND CONNECTION EXTENDING FROM THE HOUSING ADAPTED TO ENGAGETHE CONDUCTIVE SHELL OF SAID SPARK PLUG.